Most lumber used in the construction industry is known as dimension lumber, which the present invention is intended to use. Dimension lumber has opposite sides parallel, with adjacent sides forming a right angle, and is generally known by the nominal dimensions of the sides, e.g., 2.times.4, 2.times.6, 4.times.8, etc. The longer sides hereinafter are called "faces," and the shorter sides are called "edges." The pieces of dimension lumber to be processed by the present invention are called "workpieces" herein and, after cutting or processing, are called "components," e.g., rafters of several kinds, and webs and chords for trusses.
There are three kinds of rafters with which the present invention is primarily concerned:
1. "regular" rafters: PA1 2. "jack" rafters: PA1 3. "hip" and "valley" rafters: PA1 1. the distance between the outside edges of the double top plate; PA1 2. the vertical distance from the upper face of the top-plate to the ridge line; and PA1 3. the inclined, or slant, distance between the outside edge of the double top plates and the ridge line. PA1 1. FIG. 1C discloses a rafter simply laid upon the double top plate and the ridge beam, without cutting the rafter, except perhaps for a small notch at the upper end where it rests on the ridge beam: PA1 2. FIG. 1B discloses a rafter notched at both upper and lower ends to fit over the ridge beam and the double top plate, respectively. In this case: PA1 3. FIG. 1A discloses a rafter cut at both upper and lower ends to rest against the face of the ridge beam and the upper face of the double top plate, and the lower edge of the rafter intersects the lower edge of the ridge beam and the inner edge of the double top plate. In this case: PA1 1. since jack rafters have at least one end thereof cut at a composite angle, i.e., an angle both to the edges and to the faces, the lengths of opposite faces (and/or edges) thereof are unequal; and PA1 2. hip and valley rafters have at least one end which requires two cuts, both of which are at composite angles (making a compound angle) to the faces and edges, but which are usually at right angles to each other (although not necessarily). Although the lengths on the faces (or edges) may be equal, the length on the measuring line will be different (greater) than both. PA1 1. jack rafters, as disclosed in place in FIG. 2, and especially in FIG. 3, have at least one end thereof which is cut at an angle to both the edges and the faces; this is a "composite" angle; PA1 2. hip rafters, as disclosed in FIG. 2, have at least one end which requires two cuts, both at composite angles to the faces and edges; however, the cut faces usually are at right angles to each other, although they do not have to be; this is a "compound" angle; and PA1 3. valley rafters (not shown in place) have the same form as hip rafters, but are needed where two sloping roofs create a valley, and present the same problems in cutting as a hip rafter. PA1 1. a table having a plane surface normally horizontal, upon which is placed a workpiece movable along its longitudinal axis. The table: PA1 2. means for cutting the workpiece, including: PA1 3. another tiltable table, hereinafter called an "outfeed" or "second" tiltable table, having the same features as the infeed table. PA1 4. means for tipping the workpiece from its edge to its face, or vice versa, before the table is tilted; PA1 5. clamp means for holding the workpiece and the finished component during processing; and PA1 6. retractable extensions on the end of each table next to the work station, so that the workpiece is supported as it moves into and out of the work station. The extensions are retracted during cutting to avoid damage thereto or to the cutting means. PA1 1. the workpiece is placed on the horizontal surface of the first, or tiltable infeed, table, where it comes under control of the computer, and is: PA1 2. the work station includes a cutting means (e.g., a rotary saw with its rotational, or cutting, plane normal to the horizontal), which is: PA1 3. upon completion of the first cut, the cutting means is withdrawn to its initial position; PA1 4. the workpiece is: PA1 5. the cutting means is: PA1 6. upon completion of the second cut, the cutting means is withdrawn to its initial position; PA1 7. the workpiece is: PA1 1. the position and movement of the workpiece, including the starting, stopping, and distance travelled therebetween; PA1 2. the various angles and tilts; PA1 3. the thickness of the cutting means (e.g., saw kerf, water or steam jet, etc.); PA1 4. after operating on these data, it sends appropriate control signals to the various means for moving, clamping, tilting, and adjusting, to obtain a component of predetermined length along its longitudinal axis between the surfaces of the ends thereof, which have simple or predetermined composite angles at one or both ends.
those which intersect their support or supported members, i.e., plates or ridge beams, respectively, at right angles to the faces, but at an angle to the edges thereof; PA2 those which, at one end, intersect at least one of their support or supported members at something other than a right angle to each of the faces and edges of the rafter, requiring a cut at what is called hereinafter a "composite" angle on that end of the rafter; and PA2 those which intersect their support or supported members where two or more come together at an angle, requiring two cuts, called hereinafter "compound" cuts, on that end of the rafter, one or both of which may be composite angles. The angle at which the support or supported members come together is often, but not always, a right angle. PA2 a. the "measuring line" runs along the lower edge of the rafter; and PA2 b. the "ridge line" is at the bottom of the rafter where it meets the adjoining or complementary rafter. PA2 a. the "measuring line" runs parallel to the rafter's lower edge, from the outer upper edge of the double top plates to the center line of the ridge beam above its upper edge; and PA2 b. the "ridge line" is at the intersection of the two rafter measuring lines. PA2 a. the "measuring line" runs parallel to the lower edge of the rafter, from the outer upper edge of the double top plates to the point of intersection of the measuring line with the face of the ridge beam; and PA2 b. the "ridge line" runs down the midpoint of the ridge beam intersecting the projection of the measuring line. PA2 a. includes, on the surface thereof, extending parallel to the longitudinal axis, a barrier or fence against which the workpiece is held as it is being moved and cut; PA2 b. is tiltable from the horizontal along a tilt axis in the surface of the table, parallel to the longitudinal axis, to obtain a first angle of workpiece orientation; and PA2 c. includes means for moving the workpiece lengthwise along its longitudinal axis; PA2 a. means for orienting the cutting means to a second angle with respect to the workpiece, by rotating it about a second or pivot axis, preferably perpendicular to the horizontal and passing through the table tilt axis; and PA2 b. means for moving the cutting means across and through the workpiece, thereby cutting it at a predetermined composite angle composed of the first and second angles. PA2 a. tipped about its longitudinal axis from its face to its edge, or vice versa, to secure the optimum orientation for the subsequent operations; PA2 b. tilted to a first angle to the horizontal, by tilting of the first table about a first, tilt axis parallel to, but displaced from, the longitudinal axis of the workpiece (The outfeed table is also tilted to the same first angle, at this time or during the cutting operation, but prior to the movement of the workpiece to the outfeed table); and PA2 c. moved lengthwise along the longitudinal axis of the workpiece into a work station, and clamped; PA2 a. rotated about a second, pivot axis inclined and preferably perpendicular to the horizontal and passing through the first or tilt axis, to a second angle thereto; and PA2 b. drawn across the workpiece at the second angle, cutting it at a first predetermined composite angle, the resultant angle determined by the first angle and the second angle; PA2 a. moved lengthwise a predetermined distance along its longitudinal axis through the work station to the outfeed table, which is tilted to receive it; PA2 b. clamped; and PA2 c. tilted to a third angle to the horizontal, by tilting of the second table and also, in unison, the first table depending on the length of the workpiece, about the first or tilt axis; PA2 a. rotated about the second or pivot axis to a fourth angle; and PA2 b. drawn across the workpiece at a fourth angle, cutting it at a second predetermined composite angle, determined by the third angle and the fourth angle; PA2 a. moved a second predetermined distance lengthwise along its longitudinal axis to an ejection point; and PA2 b. the second table is tilted clockwise, the collapsible fence is collapsed, the clamp is released, and the workpiece is allowed to slide off the outfeed table to a receiving means.
FIG. 2 illustrates each of these kinds of rafters.
The present invention is also useful in cutting all of the webs and chords for a single truss in one operation. Formerly, an individual component for a number of trusses had to be made up at the same time, to reduce the amount of hand adjustment, and therefore cost, per component. Otherwise, it became very expensive to produce them for a single truss, since adjustments had to be made between the cutting of each different component.
To lay out a roof structure, certain distances must be accurately known:
It will help in understanding the following discussion to refer to FIGS. 1A-C of the drawings herein, which disclose three typical arrangements of rafters and their associated support or supported members, and will help to illustrate the concepts of "measuring line" and "ridge line":
The first structure of FIG. 1C is an older method of construction little used at the present time.
The second and third structures of FIGS. 1B and 1A represent methods of construction which are more widely used at present.
Regular rafters, i.e., those on which the ends are cut at right angles to the faces (or the edges), even though the ends may be cut at something other than a right angle to the edges (or the faces, respectively), do not present a great problem to manufacture, since the length of a given rafter as measured on one face (or edge) is the same as the length measured on the other face (or edge).
However, hip, valley, and jack rafters present a more difficult problem of manufacture:
Present machinery for making cuts to produce composite or compound angles on roof structure components still requires substantial hand labor in the set-up and/or operation of cutting equipment.
U.S. Pat. No. 3,568,739 teaches the use of a gauge mounted on a table-top fence to tilt the lumber so that the saw blade remains vertical when making the compound cut. A disadvantage of this method is that the measuring line of the lumber shifts laterally across the table top and shifts vertically as the gauge length is changed for different roof slopes, causing the reference point for length measurement to change. This shifting makes the gauge method inaccurate for making precision compound or composite angle cuts using a push-feed system.
U.S. Pat. No. 4,545,274 teaches a means of tilting the axis of travel of a saw blade to correspond to the complement of the roof slope, and then angling the saw blade to make the compound cut. Lumber is moved past the cutting station in a sideways manner. A separate cutting station is required for cuts on the other end of the component and, to cut components of differing lengths, one of the cutting stations must be movable in relation to the other, which takes time. Further, the cutting process is not automatic.
There is no known machinery presently available to sequentially and automatically make the cuts necessary to achieve composite and compound angles. Further, there is no known machinery presently available to automatically make the sequential angled cuts to make all of the webs and chords for a single truss without intermittent manual adjustment of machinery during the process.